Radio-phonograph combination



March 28, 1950 E. E. CAMPBELL RADIO-PHONOGRAPH COMBINATION Filed Feb.14, 1947 mm H *Q i atented Mar. 28, 1950 al-UNITED STATES PATE N-T- omennAmo-rnonozfii i r ooMBiNA'rioii v v I Eldon Earl Campbell, Chicago,11]., assignor of one-half to James Cikanek, Chicago, Ill.

Application February 14, 1947', serial No. 728,404;

1 Claim.

ducing apparatus and particularly to radio and phonograph combinationsets where the phonograph; starting switch is automatically opened atthe end of the record playing.

In the conventional combination radio and phonograph set it is necessaryto turn-a knob for changing from radio to phonograph and subsequentlythe starting switch must be closed. In changing from phonograph to radioagain a knob on the face board must be turned and subsequently thestarting switch must be opened.

It is, therefore, an object of the invention to provide a set whichautomatically changes from phonograph to radio and vice versa.

It is a further object to provide a combination set wherein the changefrom phonograph to radio is automatically efiected upon cessation of therecord playing.

A still further object constitutes the provision of a set wherein uponclosing the starting switch of the phonograph the radio circuit isdisassociated from the amplifying and reproducing equipment and uponopening of the starting switch the phonograph is disassociated from saidequipment.

It is a further object to provide means for interrupting the platecurrent of the radio frequency tubes upon operation of the phonograph sothat the life of the radio frequency tubes is lengthened.

It is a still further object to constantly heat the filaments eventhough the plate current of the radio frequency tubes is interrupted sothat the radio is in instant operation when switching from phonograph toradio.

With these and other important objects in view which will becomeapparent from the disclosure of the invention, the latter comprises themeans described in the following specification particularly pointed outin the claim forming a part thereof and illustrated in the accompanyingdrawing, which is a fundamental diagram of a radio circuit showing themechanism for automatically changing over from radio to phonograph andvice versa.

In describing the invention only those parts are referred to which arenecessary for an understanding of the invention.

The demodulator or detector'tube It. is connected by a wire I I to thesecondary l2 of the last radio frequency transformer whence a wire l3leads to a resistor l4 and then to a contact l5 adapted to be engaged bythe blade I6 of a double throw switch. The othe contact 18 is Theinvention broadly relates to sound reproconnected by a w t0 h phonogr phtone arm 20 and a wire 2l' leading therefrom is grounded to complete thecircuit.

The double throw switch I! is connected to a pull spring 22 on one sideand is controlledby an electro-magnet coil 23.

The second switch blade 24 is adapted to selectively engage the contacts25 and 26.

A wire 21 leads from contact 25 to all high voltage taps preceding thesecond detector stage.

A wire 28 is connected to a resistor 29 which is grounded as at 30.

This resister is for the sole purpose of maintaining constant voltage onoutput tube 40 regardless of whether tonearm circuit or radio circuit isoperated.

The blade I6 is connected by a wire 3] to the resistor 32 of the volumecontrol mechanism. A blocking condenser 33 is connected to the resistor32 and to the grid 34 of the sound detector.

The switch blade 24 is connected by a wire 35 to the high voltage platesupply as at B.

The electromagnetic coil 23 is connected by wires 36 and 31 to the A. C.supply of 110 volts, cycles.

A starting and stopping switch 38 is in series with the coil 23 and amotor 39 is connected in parallel with the relay circuit.

The switch 38 automatically opens at the end of the record playing, asis now incorporated in numerous record changers on the market.

In operation upon closing the starting switch 38 the circuit through themotor 39 is closed and simultaneously the relay 23 is energized and thespring tension overcome closing the switch I? with contacts 18 and 26.The switch I! closes then the circuit through the tone arm 20 and theresistor 29 which is designed to dissipate the exact amount of currentused by the radio circuit preceding the demodulator or detector.

Due to the resistor '29 the high voltage is retained at the same levelas when the radio is playing.

This is necessary because when the switch blade leaves contact 25 highvoltage is removed from all tubes of radio not actually in use forrecord playing and the same amount of current is consumed by theresistor 29 as is necessary for the radio tubes which are taken out uponenergizing the electro-magnetic coil or relay 23.

The tone arm 20 is also connected through volume control to the audioamplifying system of the radio circuit following the second detector upto the loud speaker.

The life of the radio frequency tube is lengthened because during theplaying of the phonograph these tubes are not conducting current sincethe plate voltage is removed.

The filaments, however, are constantly heated so that upon changing overfrom phonograph to radio the latter is instantly in operation since notime lapse is necessary for the normal heating period of the filament.

When the last record is played the phonograph automatically stops andsimultaneously the starting switch is automatically opened as is wellknown by those versed in the art.

Upon the opening of the starting switch 38 the motor 39 and the coil 23are de-energized. Thereupon the spring 22 causes the switch to engagecontacts I5, 25, cutting out the resistor 29 and returning high voltageto the radio cir-- cuit section preceding the audio stages.

I claim:

In a combination radio-phonograph apparatus of the known type includingat least an audio amplifying section, a'radio frequency section, ademodulating section, a source of plate potential, a phonograph tonearm, and a phonograph motor and a starting switch therefor, improvementscomprising, to wit: a relay having its winding shunted across theterminals of said motor for energization when said motor is running,normal contacts on said relay and closed when the latter is deenergizedto complete an operating circuit between said demodulating and audioamplifying sections, and to connect said radio frequency section to asource of plate potential, said relay having contacts closed uponenergization to connect said audio amplifying section to said tone armand to connect a standby load to said source of plate potential.

ELDON EARL CAMPBELL.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,768,658 Balsley July 1, 19301,768,661 Brindley July 1, 1930 1,811,856 Long June 30, 1931 1,852,877Gardner Apr. 5, 1932 1,852,878 Gardner Apr. 5, 1932 1,969,344 AndrewsAug. 7, 1934 2,405,526 Sinnett Aug. 6, 1946

